I want to make Forward and Backward Slack Activity on Node Diagrams in MS Project 2010.

I display the Network Diagram view and choose Format > Box Styles. I Click the More Templates button and in the Data Templates, dialog, select an existing template and copy it. I Give the new template a name in the Data Definition dialog window. Towards the bottom of the Data Definition dialog window in the "Choose Cells" section I can specify which fields to place in which area.

I want to define four custom number fields ES, LS, EF, and LF.

ES = ProjectDateDiff([ProjectStart],[EarlyStart])/[MinutesPerDay]

EF = ProjectDateDiff([ProjectStart],[EarlyFinish])/[MinutesPerDay]

LS = ProjectDateDiff([LateStart],[ProjectFinish])/[MinutesPerDay]

LF = ProjectDateDiff([LateFinish],[ProjectFinish])/[MinutesPerDay]

but it seems MS Project doesn't allow formulas or custom fields.

How can I do a formula in a box field or formula ? Is it possible ?

  • 1. The ProjectDateDiff funtion is fine for vba but will generate a syntax error in custom field formulas. (Use ProjDateDiff.) (In the absence of an explicit calendar specification, the two functions may yield different results in the presence of task calendars or elapsed-duration tasks.)
    – Tom Boyle
    Jul 16, 2020 at 15:49
  • 2. Your ordinal-date definition is unconventional, yielding forward-pass dates beginning with zero and ending one less than the project duration. Also, measuring your late-date ordinals from the Project Finish date can be misleading. (Conventional terminology has the project starting on day 1, with all other ordinal dates referenced to this.) Any calendars and milestones will interfere with this.
    – Tom Boyle
    Jul 16, 2020 at 15:58
  • Where can I find a list of formula and variables project uses such as ProjDateDiff ?
    – user4434
    Jul 19, 2020 at 19:39

1 Answer 1


No, it's not possible to use formulas directly in the field selector for the network box templates. Instead, use formulas to populate custom number fields for the ES, EF, LS, and LF ordinals. Then select these custom fields for the box template.

  • Okay, how to do I use formulas to populate the custom number fields for ES, EF, LS and LF ? Where can I do that in Project ? I can't seem to find where it is...
    – user4434
    Jul 16, 2020 at 17:48
  • In MSP 2010, click the Custom Fields button on the Properties group of the Project Ribbon. Choose 4 task number fields, renaming and entering your formula for each.
    – Tom Boyle
    Jul 16, 2020 at 19:51
  • are the formulas as i entered above admissible into ms project or not ?
    – user4434
    Jul 16, 2020 at 20:50
  • No they are not. Haven't you tried them? To avoid all syntax errors, use the pick-lists for functions and field names that are included in the formula-building dialog in MSP. You also need to fix the underlying issues with your algorithm. (Sorry for the reticence - only limited help for school assignments.)
    – Tom Boyle
    Jul 17, 2020 at 12:34
  • not looking for assignment help. just trying to figure out how to put formulas. i will put some screen shots here and see if i am on the right track.
    – user4434
    Jul 18, 2020 at 5:22

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